The High Speed Cell Sorter Core (HSCS Core) provides the following services: 1. Cell sorting. A three laser, high speed cell sorter (MoFIo, DakoCytomation, Inc.) with a flexible configuration is housed in the HSCS laboratory. Dedicated technicians in the Core are responsible for all aspects of instrument operation. 2. Flow cytometric analysis. A three-color benchtop analytical instrument (BD FACScan) is available in the HSCS Core laboratory for self-service or supervised use by SCC members. 3. Sample preparation. For investigators lacking suitable infrastructure to prepare samples for flow cytometric analysis, the HSCS Core provides a range of technical assistance from experimental design to cell isolation, staining, and analysis. Flow cytometry is a powerful tool widely utilized in clinical oncology and cancer biology research. The HSCS Core was established to serve a growing number of investigators at the Washington University School of Medicine whose needs were not adequately met by existing cell sorting facilities on campus. A shared instrumentation grant from the NCRR provided funds for the purchase of a high speed cell sorter. Additional hardware and software were acquired with support from the SCC. The core is now a fully equipped state-of-the- art facility that strives to improve the quality of flow cytometry research performed in the SCC by assisting investigators in all phases of their experiments from planning to publication.